Today's telephony devices are becoming increasingly more sophisticated. A driving force of this trend is the convergence of functionality typically found in computers with functionality found in conventional telephones. One significant example of the convergence of phones and computers is a class of devices called screen phones. Though the specific hardware configuration of these devices varies widely, they typically share common elements such as a screen display, hardware buttons, telephone line interface hardware and a processor. Despite the advanced features that many of these devices provide, there is still need for improvement in many areas.
First, some screen phones available today have a small text-based display, typically arranged in a matrix of characters, and hardware buttons around the screen that are associated with specific screen areas to create virtual or soft buttons. This allows new functions to be programmed in to the buttons over time, or as a result of navigating through menu choices with the buttons. Usability testing and research have shown that the mapping of a physical button and the on-screen text is often confusing and hard to follow.
Another problem is that traditional enhanced telephony services are difficult to use (such as call forwarding) because they require the user to remember arbitrary sequences of key-presses, and remember sequences of operations without explicit feedback (feedback tones or clicks).
An additional problem with the screen phone industry is the lack of an extendable, flexible software architecture that allows others to build a rich array of functions and application programs. Screen phones tend to be highly specialized devices constructed with special hardware and software to support a set of features. As such, they are difficult to customize or extend to support new features.
This lack of flexibility is particularly problematic in view of the lack of uniformity in the telephone network—where infrastructure components vary from region to region, country to country, and service provider to service provider. Each area may provide Caller ID, but these areas may supply it using different technologies, or supply Call Forwarding, but use different access codes.
The problems associated with architectural flexibility extend beyond the challenges raised by differences in central office switching, hardware, and configuration. The underlying telecommunication network infrastructure is changing as well, and telephony devices must be adaptable to these infrastructures. For example, the telephone architecture should support choices between conventional infrastructures such as PSTN and ISDN. Looking to the future, the use of the Internet Protocol may become more commonplace as a telephone network infrastructure, and thus, there is a need to make telephony architectures readily adaptable to a variety of network infrastructures.